Mortgage Loans TDRs with Sub Defaults (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) contracts	Mar. 31, 2019 USD ($) contracts
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contracts	3,561	5,159
Recorded investment troubled debt restructurings subsequent default | $	$ 578	$ 777
Single-family [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contracts	3,559	5,159
Recorded investment troubled debt restructurings subsequent default | $	$ 576	$ 777
Single-family [Member] | Fixed Rate Residential Mortgage 30 and 20 year Member
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contracts	3,175	4,376
Recorded investment troubled debt restructurings subsequent default | $	$ 521	$ 664
Single-family [Member] | FixedRateResidentialMortgage15yearMember
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contracts	50	132
Recorded investment troubled debt restructurings subsequent default | $	$ 3	$ 8
Single-family [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contracts	327	643
Recorded investment troubled debt restructurings subsequent default | $	$ 51	$ 104
Single-family [Member] | Adjustable Rate Residential Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contracts	7	8
Recorded investment troubled debt restructurings subsequent default | $	$ 1	$ 1
Multifamily [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default | contracts	2	0
Recorded investment troubled debt restructurings subsequent default | $	$ 2	$ 0